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Biomedical subjects

D Norman

Publications and source records attributed to D Norman.

At least 199 records · Page 11Linked to original sources
PubMed1985

Central nervous system tumors in children: detection by magnetic resonance imaging.

Fifty-one pediatric patients who were suspected of having central nervous system (CNS) tumors underwent magnetic resonance (MR) imaging using a 0.35 T Diasonics MT/S system. Pulse intervals (TR) ranged from 0.5 to 2.0 seconds with echo delays (TE) of 28 and 56 msec. The ability of MR and contrast-enhanced CT to detect focal lesions, determine lesion extent, and evaluate associated abnormalities was compared. In most patients in whom there was suspected spinal cord disease, comparison with myelography was made. Thirty-three intracranial lesions were detected with at least one imaging modality in 43 cranial examinations. MR was judged superior to CT in 14 of these cases and CT superior to MR in only one. Of eight spinal examinations, there were six that demonstrated abnormal findings. MR was superior to CT in all six cases and better than myelography in four of five cases where myelography was performed. Spin echo (SE) sequences with long pulse intervals were the most sensitive, but in some cases short pulse intervals permitted further characterization of the lesion. Patient motion was not a problem; sedation was routinely used in children younger than five years of age. MR imaging has rapidly become a valuable diagnostic modality in neuroradiology. The lack of ionizing radiation and the ability to evaluate the spinal cord noninvasively makes it particularly attractive in examination of children.

Adolescent↗
PubMed1985

Cystic intracranial lesions: magnetic resonance imaging.

Thirty-three patients with cystic intracranial lesions were examined with both magnetic resonance (MR) imaging and CT scanning. The abnormalities imaged included 11 arachnoid cysts, 10 cystic tumors, six postoperative cysts, and three colloid cysts. The intensity patterns of the cyst contents as encoded with routine spin-echo imaging sequences enabled subdivision of the cysts into three categories. Arachnoid and postoperative cysts had an intensity pattern identical to cerebrospinal fluid. More proteinaceous cysts, including inflammatory cysts and nonhemorrhagic tumoral cysts, had an intermediate intensity pattern with characteristically low intensity on the short TR sequence (0.5 sec), but had clearly higher intensity than cerebrospinal fluid on the long TR sequences (2 sec). Finally, three cystic tumors with hemorrhagic fluid and three colloid cysts had a distinctly different pattern of high intensity on all four MR sequences through the same section. MR was superior to CT in characterizing intracranial cystic lesions because of its ability to categorize cysts into these three groups on the basis of the intensity pattern of cyst contents, thereby improving diagnostic specificity and patient management.

Adolescent↗
PubMed1985

Intraarterial digital subtraction imaging cost considerations.

In an attempt to quantitate the cost-effectiveness of digital arterial imaging, we compared our real costs for angiographic procedures during a 6-month period with the costs for digital arteriographic imaging after the procedure was well established and accepted by both radiologists and clinicians. This study based on 400 angiograms per year, revealed that use of a digital angiographic unit resulted in an 82% reduction in film costs, a 25% reduction in staffing costs, a 19% reduction in the time required per examination, and a 30% reduction in the time required per run. Thirteen percent more runs were performed with the digital unit because it was more convenient and had a limited field of view. Overall operating cost savings were 43%. If amortized additional capital costs are included, there is a 12% reduction in overall costs. The digital imaging unit provides an immediate cost savings, with no appreciable loss of diagnostic quality. In addition, patient comfort, and perhaps safety, are improved.

Angiography↗
PubMed1985

Intracranial vascular malformations: MR and CT imaging.

Twenty-four patients with 29 cerebrovascular malformations were evaluated with a combination of computed tomography (CT), angiography, and magnetic resonance (MR) imaging. Characteristics of the malformations on MR images were reviewed retrospectively, and a comparative evaluation of MR and CT images was made. Of 14 angiographically evident malformations, 13 intra-axial lesions were detected on both CT and MR images, and one dural malformation gave false-negative results on both modalities. The appearance of parenchymal lesions on MR images closely mirrored characteristic CT findings. Calcific foci were difficult to separate from vessels on both images. Clot was more easily identified on MR images. In the detection of 15 angiographically occult malformations, CT proved more sensitive when focal calcification was the only evidence of their presence. MR study failed to detect two small supratentorial lesions evidenced by faint calcifications on CT scans. In two patients, MR images showed small hemorrhages not detectable by CT, and MR provided strong evidence for the diagnosis of hematoma for 12 lesions. Angiographically evident malformations have a highly characteristic appearance on MR images. MR may be more sensitive than CT in the detection of small hemorrhagic foci associated with cryptic arteriovenous malformations and may add specificity in the diagnosis of occult malformations in some cases, but MR is less sensitive than CT for the detection of small calcified malformations.

Adolescent↗
PubMed1985

MR technology: effect of even-echo rephasing on calculated T2 values and T2 images.

In multiple spin-echo image sequences of blood flow, the "even-echo" phenomenon produces an absolute increase in signal magnitude from first- to second-echo images of normal vessels harboring slow flow. Distinguishing this from the apparent relatively high signal intensity seen on second-echo images in pathologic foci of stationary tissue is important to the diagnostician. Selected case material containing two tissue types was reviewed retrospectively: tissues known to harbor slow flow, such as normal veins and venous sinuses and vascular malformations, and tissues that have long transverse (T2) relaxation times and appear as intense structures on second-echo images, such as neoplasms, infarcts, and regions of demyelination. Calculations of T2 parameters were made by computer for defined regions of interest. T2 images were also generated. Visual inspection of the acquired images did not reliably distinguish increased intensity due to even-echo rephasing from the relative changes between adjacent tissues seen on second-echo images. More definitive differentiation of the even-echo phenomenon was provided by calculated values of T2 and computer-synthesized T2 images representing acquired intensity data of two-echo sequences. The synthesized images were especially useful when stationary tissue with lengthened T2 values was adjacent to or in proximity to vessels or vascular lesions. A five spin-echo image sequence was valuable for separating slow flow from stationary tissue by a technique of synthesizing T2-difference images using three consecutive echoes.

Brain Diseases↗
PubMed1985

MR imaging of calcified intracranial lesions.

Fifty calcified intracranial lesions diagnosed with computed tomography (CT) were evaluated with magnetic resonance (MR) using a spin-echo sequence. MR images demonstrated 41 of 50 lesions seen as calcified on CT scans, among them 29 of 30 cerebral neoplasms and all ten arteriovenous malformations. The presence of calcification was suspected prospectively in about 60% of calcified lesions but was also suspected in 45% of uncalcified lesions (reviewed as control cases). No fine calcifications and only 25% of punctate calcifications were disclosed on MR images. In the nine lesions undetected by MR, calcification was the only abnormal CT finding. The findings of calcification on MR images were nonspecific, ranging from signal void or signal dampening on all sequences to no alteration of signal intensity. The most common finding of calcification was a focus of signal diminution, rather than signal void, as commonly reported.

Adolescent↗
PubMed1985

Amikacin + ceftazidime therapy of experimental right-sided Pseudomonas aeruginosa endocarditis in rabbits.

We investigated the efficacy of a potent new antipseudomonal beta-lactam agent, ceftazidime, in a model of right-sided Pseudomonas endocarditis in 72 rabbits. Animals received either: no therapy (controls), amikacin (15 mg/kg/day), ceftazidime (100 mg/kg/day) or amikacin + ceftazidime. Amikacin + ceftazidime was significantly more effective than single-drug regimens in terms of reduction of mortality (p less than 0.01), prevention of pulmonary infarction (p less than 0.05), reduction of mean vegetation titers of Pseudomonas aeruginosa (p less than 0.05-p less than 0.0005), sterilization of vegetations (p less than 0.0005) and reduction in prevalence of bacteriologic relapses after therapy (p less than 0.005). There was no development of resistance in vivo to either amikacin or ceftazidime.

Amikacin↗
PubMed1985

Metrizamide CT myelography in cervical myelopathy and radiculopathy: correlation with conventional myelography and surgical findings.

Conventional myelography, metrizamide computed tomographic (CT) myelography, and surgical findings were correlated in 30 patients with cervical radiculopathy and/or myelopathy. In 60% of patients, metrizamide CT myelography provided significant additional information including better characterization of the abnormality, lateralization if the conventional myelogram was indeterminate, more definitive demonstration of cord atrophy, foraminal narrowing not appreciated on myelography, and demonstration of abnormalities distal to a myelographic block. In no case was a myelographic abnormality not detected on metrizamide CT myelography. In patients with cervical myelopathy, a cross-sectional diameter of the cord equaling less than 50% of the subarachnoid space is predictive of poor patient response to surgical intervention.

Adult↗
PubMed1985

Reproducibility of relaxation times and spin density calculated from routine MR imaging sequences: clinical study of the CNS.

This study was undertaken to determine if routine clinical magnetic resonance imaging sequences using only two different repetition times (TRs) and with only two sequential spin echoes (SEs) can be used to calculate reproducible relaxation time and spin density values for normal central nervous system tissue using a 0.35 T production-model instrument. In 43 patients 650 regions of interest of 11 different anatomic sites were measured. T1 and T2 relaxation times and spin density were measured. For each anatomic location, the mean and standard deviation of these values were determined. In most solid regions of brain, the standard deviation of both T1 and T2 was 4%-8%. Relaxation times of cortical gray matter varied more, with a standard deviation of 10%, probably because of volume-averaging with adjacent cerebrospinal fluid (CSF). CSF and ocular vitreous humor were neither reproducibly nor accurately measured because of the short TR and TE settings of the imaging sequences relative to the long T1 and T2 relaxation times of these substances. Significant and reproducible differences were found between the spin densities of gray matter and white matter, as well as between different regions of white matter. These differences are of major importance in contrast discrimination of gray and white matter on the long TR images. Knowing that relaxation values and spin densities calculated from routine imaging sequences are in fact reproducible, these normal ranges can now be used to investigate changes occurring in disease states.

Adolescent↗
PubMed1985

Outpatient DSA in cerebrovascular disease using transbrachial arch injections.

Experience with intravenous digital subtraction angiography (DSA) has proven disappointing in the outpatient evaluation of cerebrovascular disease. Vessel superimposition, patient motion, and poor vascular opacification all prevent definitive studies in a significant percentage of patients. These problems were addressed by turning to an intraarterial outpatient DSA technique composed of several elements: (1) right transbrachial catheterization of the ascending aorta using a thin, multiple side-hole, straight catheter; (2) arch injections of relatively small volumes of contrast material; (3) pulsed digital image acquisition with multiple projections; and (4) a limited period of postprocedure observation. A total of 43 outpatients and 16 inpatients was studied in this manner with only two complications, both local. Images of definitive quality and completeness were obtained in 82%-98% of cases, and included the major intracranial as well as the extracranial vessels and their circulatory dynamics. Because the iodine load per injection was relatively low, up to 10 angiograms per case were available for delineating superimposed anatomy and motion degradation. Variations in cardiac output had little impact on image quality, and the average case required less than 60% of the contrast load routinely used for intravenous DSA. The transbrachial approach proved as safe and convenient as intravenous DSA but was more thorough and dependable.

Adult↗
PubMed1985

Localization studies in patients with persistent or recurrent hyperparathyroidism.

Preoperative localization studies are essential for patients who have undergone previous parathyroid operations. This is because the remaining parathyroid glands are more difficult to identify at operation because of increased scarring with loss of normal tissue planes and because the remaining abnormal parathyroid tissue is more likely to be situated in an ectopic position. This investigation concerns the accuracy of preoperative localization studies in 36 consecutive patients. All patients had symptoms and clinical and laboratory data diagnostic of primary (31 patients) or secondary (five patients) hyperparathyroidism. Ultrasonography was performed in all 36 patients; 18 (50%) were positive, 14 (39%) were negative, and four (11%) were false positive examinations. Eight of the negative study results occurred in patients with abnormal parathyroid glands situated in the mediastinum. Computerized tomography (CT) was performed in 25 patients. There was an equal number of positive (11; 44%) and negative (11; 44%) studies with three (12%) false positive test results. CT was helpful in identifying substernal lesions and other abnormal parathyroid glands situated in ectopic positions. Thallium chloride 201-technetium 99m pertechnetate scans were used in 22 patients. There was an equal number of positive (eight; 36%) and negative (eight; 36%) studies. Six patients (27%) had false positive scans. One or more of these noninvasive tests was positive in 27 of the 36 patients (75%). Highly selective venous catheterization for the measurement of immunoreactive parathyroid hormone concentrations localized the elusive parathyroid tumor in 12 of the 16 patients (75%) overall and in six of the nine patients (66%) whose tumors were not identified by other studies. One patient had both a false positive ultrasound and thallium chloride 201-technetium 99m pertechnetate scan. Preoperative localization studies were therefore very helpful for locating hyperfunctioning parathyroid glands in patients with recurrent or persistent hyperparathyroidism, and 75% of the tumors were identified by noninvasive studies. Seventy-five percent of the tumors not identified by noninvasive studies were localized by selective venous catheterization. Most tumors not identified by noninvasive studies were mediastinal or ectopic in position.

Adult↗
PubMed1985

Magnetic resonance imaging of the central nervous system--an update.

Magnetic resonance imaging has developed rapidly and now has superior ability to detect and to characterize disease in the central nervous system without any significant biologic hazard. It is becoming the screening method of choice in the diagnosis of neoplasm, ischemia, hemorrhage, infection and degenerative and demyelinating diseases involving the central nervous system.

Central Nervous System Diseases↗
PubMed1985

Magnetic resonance imaging of the central nervous system.

Clinical MRI of the CNS has evolved rapidly. The image quality has now surpassed CT in depicting anatomical detail. It is more sensitive than any other imaging modality, including CT, in the detection of disease. The specificity of MR is at least equivalent to CT, and as the learning curve improves and a broader base of information is acquired as to the relative utility of different imaging parameters and the applications of T1 and T2 measurements, it is hoped that specificity will improve as well. There is little question that in the cooperative patient MR will displace CT scanning as the primary screening modality in the patient with CNS disease in whom an imaging technique is appropriate.

Brain Neoplasms↗
PubMed1984

Influence of acute tubular necrosis on first cadaver kidney transplant function.

Prolonged cold storage following intracellular electrolyte flushing increases the probability of significant acute tubular necrosis after cadaver kidney transplantation. The renal function of primary cadaver kidney grafts was compared in 68 recipients who required dialysis and 92 who did not require dialysis during the first week after transplantation. All kidneys were retrieved from beating-heart cadaver donors by our center, flushed with ice-cold intracellular electrolyte solution and cold-stored until transplantation at our hospital. Recipients requiring dialysis during the first week after transplantation received kidneys with a significantly longer cold storage time (27.4 plus or minus 10.2 versus 23.2 plus or minus 7.6 hours) and had significantly higher 1-month serum creatinine nadirs (2.1 plus or minus 1.3 versus 1.5 plus or minus 0.6 mg./dl.). Actuarial kidney graft survivals and serum creatinine levels 1 to 5 years after grafting were not significantly different. Acute tubular necrosis following primary cadaver kidney transplantation does not adversely affect long-term function of kidney grafts flushed with intracellular electrolyte solution and cold-stored until transplantation.

Acute Kidney Injury↗
PubMed1984

Retinoblastoma. CT diagnosis.

Computed tomography (CT) scan is a valuable adjunct in the differential diagnosis and management of retinoblastoma. Thirty-one of 33 retinoblastoma patients studied with high resolution computed tomography had intraocular calcification demonstrable in at least one eye. Over 80% of tumors showed evidence of calcification on CT scan. The degree of calcification appeared to depend upon tumor size; only small tumors were devoid of calcification. The amount and distribution of calcification was similar on both histological and CT review. In patients under three years of age in whom a retinoblastoma is suspected, the presence of calcification on CT scan is virtually diagnostic of retinoblastoma; patients with leukocoria without calcification on CT probably have a simulating lesion.

Calcinosis↗
PubMed1984

Primary intracranial tumor imaging: a comparison of magnetic resonance and CT.

Twenty-six patients with primary intracranial tumors were evaluated by magnetic resonance (MR) and a comparison was made with CT findings. The SE technique with TR = 2,000 ms and TE = 56 ms was most useful in delineating normal anatomy, in differentiating gray and white matter, and in optimizing the visualization of edema. The use of TR = 500 ms optimized sensitivity to T1 relaxation time differences in disparate tissue and best defined the cerebrospinal fluid spaces. Although prolongation of T1 and T2 relaxation values was seen with most malignant lesions, several cases produced no obvious prolongation of T1. Separation of tumor from surrounding edema was possible in several instances. In 16/26 patients information not available on CT was obtained with MR. This included detection of altered tissue characteristics where CT showed only mass effect, more accurate depiction of full extent and location of tumor, and visualization of associated abnormalities. However, a small inner ear epidermoid tumor seen with high-resolution CT (1.5-mm sections) was difficult to identify with certainty on MR, and in two other cases punctate foci of calcification were not identified on MR.

Adolescent↗
PubMed1984

Orbital tumors in children. Characterization by computed tomography.

CT characteristics of orbital masses in 39 children were reviewed. Histological types and their relative frequencies differed considerably from reported adult cases. Analysis of seven separate CT characteristics for each type of mass indicated certain trends which may aid in the differential diagnosis.

Adolescent↗